[SAGE] Experiences with PeerFS?

[Ben Poliakoff <benp@reed.edu>]

Hi All,

Has anyone on this list evaluated (or is anyone actually using) Radiant
Data's PeerFS filesystem?

    http://radiantdata.com/English/Products/PeerFS.html

BEGIN summary

It's a proprietary replicated filesystem for Linux that seems to combine
some of the features of a cluster filesystem, as well as a network block
device; it supports as few as 2 and as many as 64 nodes.  A replicated
volume is stored on each nodes' local disk.

Read operations use the local disk, write operations consult the
cluster.  The vendor claims that PeerFS provides "POSIX file locking
operations", so that applications don't need to be rewritten to use the
filesystem.

A node can be disconnected from the cluster at any point (when
disconnected it is read-only).  While disconnected the frozen filesystem
can be used for performing backups.  When the node is brought back into
the cluster the replicated volume is "re-integrated".

A new node can be added to the cluster at any point.  The replicated
filesystem is immediately available.  

>From the white paper:

    What actually happens is that PeerFS will start up a background
    synchronization activity (called a consistency check) and the
    new computer will satisfy all of its I/O transactions to the
    closest and least busy consistent computer on the network. Once the
    synchronization completes, I/O activities on the new computer will
    redirect themselves back to the local storage.

END summary

At any rate.  This seems like a very interesting product.  I don't know
what the pricing model is, but I'm curious of anyone here has any
experience with PeerFS.

Ben